The present invention relates to a method for controlling microorganisms, particularly fungi and bacteria on potato tubers. More particularly, the invention relates to a method employing 2,2-dibromo-3-nitrilopropionamide (DBNPA) as the active ingredient, and in which the tubers or the seed tubers to be treated are fogged therewith.
DBNPA is a well-known biocide, useful in a number of industrial and agricultural applications. In a patent application of the same applicant there is described a method for controlling microorganisms on potato tubers and potato seeds, by the fumigation of DBNPA, which provides microorganism control with high effectiveness. Fogging of DBNPA on potato seeds, which is the subject matter of the present invention, however, has never been attempted. Fogging typically involves the suspension in air of liquid droplets from about 0.1 to about 30 microns in diameter. The mean diameter of the droplets within this range is usually from about 0.5 to about 4.0 microns, although other mean diameters of the 0.1 to 30 micron particles are also suitable for use with the present invention. Fogging differs from fumigation, which is carried out by substantially evaporating the compound involved. By conventional definition, evaporation requires a change of state from liquid to gas. Fumigation, therefore, mixes gas-phase molecules of DBNPA with air. The gas-phase molecules of DBNPA are significantly smaller than the liquid droplets of DBNPA suspended in the air by fogging.
Biocide application is often carried out by spraying. Spraying, however, differs from fogging in that it involves droplet sizes in the order of magnitude of 80-90 microns. When a biocide is applied by spraying, a large quantity - half or more - of the droplets reach the walls and the floor of the spraying chamber. Thus, the effective amount of biocide is relatively low, and relatively high total amounts of biocides are therefore required, which is a considerable drawback, especially from the economic, health and environmental point of view.